[2] Born in Kawakawa, New Zealand, Veainu went to St Andrew's College in Christchurch where in his final year of school he was made captain of the 1st XV.

For the 2013 ITM Cup, Veainu moved north to join Hawke's Bay and scored 7 tries in 11 matches for the Magpies.

For the 2013 Super Rugby season Veainu returned to his home province to sign with the Crusaders, but again struggled to duplicate his ITM Cup form, appearing in only 4 games as a substitute.

[15] Veainu played for the New Zealand U20 at the age of 18 and 19, but in 2015 he was selected for Tonga for the 2015 World Rugby Pacific Nations Cup.

Veainu was selected for Tonga's 31-man squad to attend the 2019 Rugby World Cup, by Head Coach, Toutai Kefu.

Veainu was Tonga's top try-scorer of the tournament, scoring three tries in total, two against Argentina and one in a two-point deficit to France.